Kausch



w. KAUSCH 3,048,663 STEREOPHONIC AMPLIFIER AND LOUDSPEAKER SYSTEM Aug.7, 1962 Filed Aug. 3, 1959 RADIO RECEIVER PHONO PLUG Lw FREQUENCYSPEAKER- I 1 l r VOLUME R CONTROL v6) HIGH FREQUENCY SPEAKER HIGHFREQUENCY SPEAKER STEREO PICKUP Inventor? l /e r n e r K62. Us:

3 Pa fan 2 j"! United States Patent Ofifice 3,@ i8,%3 Fatented Aug. 7,1962 3,048,663 STEREQPHONIC AMPLIFTER AND LOUD- SPEAKER SYSTEM WernerKausch, Hannover, Germany, assignor to Telefunken G.ni.b.fi., Berlin,Germany Filed Aug. 3, 1959, Ser. No. 831,122 Claims priority,application Germany Aug. 9, 1953 1 Claim. (Cl. 179l00.1)

The present invention relates to a system for reproducing stereo soundrecordings, whereby an auxiliary apparatus is used to supplement anordinary radio set or other music-reproduction device which mayalso beconnected to a turntable or to a tape recorder.

Radio sets usually are designed for monaural reproducing and, therefore,have only a single channel. Such a radio set can only. be employed toreproduce a single channel of a known stereo pickup arrangementconnected to the phono plug of the radio set to use its amplifier. Forstereo reproduction, either a dual speaker system in appropriate cabinetarrangements has to be provided or the amplifiers of two radio sets areseparately connected to one of the two stereo recording pickup channels.Obviously, this is unnecessarily expensive, beause in the reproductionof records or tapes using two radio sets, only the audio amplifiersthereof are used. Thus, the high frequency tuner portions of at leastone of the radio sets is superfluous and unused. Furthermore, when tworadio sets are used, there is a separate volume control for each of themand, usually, it is difiicult to properly adjust the balance betweenthem so as to obtain precisely the stereo effect actually intended inthe particular recording being layed back.

It is object of the present invention to provide a stereophonicreproduction system wherein an ordinary radio set or any othersingle-channel sound amplifying means can be used as the basiccomponent. This system is then supplemented by an auxiliary apparatusused for separating the higher and lower frequencies of the two stereosignals picked up separately, and after such separation to feed thehigher frequencies thereof to separate higherfrequency responsiveloudspeakers.

It is a further object of the invention to provide a stereophonicreproduction system by driving the lower frequency loudspeaker of aconventional single channel sound reproduction means, for example, anordinary radio set, and by adding an auxiliary apparatus for reproducingas a second stereo channel merely the high frequencies of the recording,whereby the volume of the stereo reproduction is controlled by a singlemeans.

It is another object of the invention to provide an auxiliary apparatusfor stereo sound reproduction which can be used together with any kindof single channel sound reproduction means having a phono input plug.

In accordance with one aspect of the invention, a stereophonicreproduction system may be designed as follows: An ordinary radio sethaving a phono input plug, two higher-frequency responsive loudspeakers,a stereo pickup, two mechanically ganged potentiometers, each oneinserted in a different output channel of the stereo pickup, a high-passand a low-pass filter for each of said channels, separate amplifiersfrom each high-pass filter to each higher-frequency loudspeaker, and acommon connection from the two low-pass filters to the phono plug of theradio.

Still further objects and the entire scope of applicability of thepresent invention will become apparent from the detailed descriptiongiven hereinafter; it should be understood, however, that the detaileddescription and specific examples, while indicating preferredembodiments of the invention, are given by way of illustration only,since various changes and modifications Within the spirit and scope ofthe invention will become apparent to those skilled in the art from thisdetailed description.

In the drawing, an embodiment of the present invention is schematicallyillustrated.

Numeral 1 designates an ordinary radio set having an amplifier capableof monaural sound production. 2 is an auxiliary apparatus according tothe invention. 3 and d are two high-frequency-responsive loudspeakersand 5 is a stereo sound pickup for record disks, tapes, or the like. Thestereo sound pickup 5 may be of any known kind, and includes two outputwires 51 and 52 and a common ground connection 53. Output wires 51 and52 are connected to impedances, such as potentiometers 31 and 41,respectively. A wiper 32 of a potentiometer 31 is ganged with a wiper 42of a potentiometer 41 and the two wipers may be operated by a commonknob (not shown), said knob rotating a mechanical shaft 21 ganging thetwo wipers together. The wiper 32 is connected to the control electrodeof an electronic amplifier tube 33, while the wiper '42 is connected tothe control electrode of an electronic amplifier tube 43. The outputs ofthe tubes 33 and 43 are fed to amplifier tubes: 34 and 44, respectively,via R-C high-pass filters 35 and 45, respectively. The output of theamplifier tube 34 drives loudspeaker 3, while the output of theamplifier tube 44 drives the loudspeaker 4.

The outputs of the tubes 33 and 43 are also fed to a common connectionpoint 22 via low-pass filters 36 and 46, respectively, and viadecoupling resistors 37 and 47, respectively. A conductor 23 from point22 is plugged into the usual sound input connector or phono plug 11 ofthe radio set 1. The loudspeakers 3 and 4, are preferably mounted inseparate baffles or cabinets (not shown) which may be placed in mutuallyspaced relation.

These higher-frequency loudspeakers may now be used to produce thedesired stereo effect. The low frequencies are fed into the radio set 1and are reproduced by the lower-frequency speaker 12 thereof. Since, asis shown in the drawing, the common connection point 22 constituting theoutput of the low-pass filters 36 and 46 is connected directly to thesound input connector 11 of the radio set 1, it is the amplifier of theradio set which is relied upon to amplify the lower frequencies, therebeing no amplifier between the output of the low-pass filters 36, 46,and the connector 11, i.e., while the higher frequencies are amplifiedby components incorporated in the auxiliary apparatus, the amplificationof the lower frequencies is left to a component pertaining to the radioreceiver. The volume control 13 of the radio set 1 regulates the volumeof the lower frequencies, while the two ganged wipers 32 and 42 regulatethe volume of the higher frequencies. Thus, there is a separate volumecontrol for high and low frequencies, thus, automatically providingseparate treble and bass controls. Even though the radio set 1 may haveseparate higherand lower-frequency loudspeakers, only the latter aredriven, due to the filters 36 and 46.

From this description, it can be seen that the invention makes use ofthe known fact that stereo reproduction is not defeated when the lowersound frequencies are initially picked up separately, but are combinedand reproduced in a single loudspeaker, and only higher frequencies arereproduced in stereo. The lower-frequency loudspeaker of a single radioset is used for this purpose and supplemented by auxiliary apparatus, asoutlined above. The lower-frequency loudspeaker reproduces substantiallyno higher sound frequencies. This approach to the problem of stereoconversion has the advantage that the auxiliary apparatus does not needto be specially adapted to the particular radio set uesd, but cancooperate with any radio or music reproduction amplifier and cabinet,because the radio set does not affect 3 the quality and the frequencyresponse of the two higher audio frequency channels.

Another advantage, as stated above, is that the two volume controlsassociated respectively with the radio set and the auxiliary apparatusare independent of each other as far as the stero effect is concerned.

Finally, there is the advanatge that one needs only a small power supplyfor the higher audio frequency reproduction apparatus, which means thatonly a small rectifier network and a small power output transformer areneeded.

I claim:

For use with a monaural radio receiver means having a speaker capable ofreproducing at least the lower audio frequencies, a sound inputconnector, and an amplifier between said speaker and said connector, anauxiliary apparatus for enabling said monaural radio receiver means tobe used as a part of a stereo sound reproduction system, said auxiliaryapparatus comprising circuit means forming two channels connectable,respectively, to two outputs of a stereo scanning device, said circuitmeans including, for each channel, a first amplifier, a high-pass filterconnected to the output of the corresponding first amplifier, and asecond amplifier connected to the output of the corresponding high-passfilter, the output of said second amplifiers being connectable toreproduction means for reproducing the higher audio frequencies, saidcircuit means further including two low-pass filters branching from saidchannels and connected to a common output which itself is connectabledirectly to the sound input connector of the monaural radio receivermeans with which the auxiliary apparatus is used, and said circuit meansfurther including two volume controlling means in said two channels,respectively, said two volume controlling means being mechanicallycoupled to each other, whereby the higher frequencies are amplified bycomponents incorporated in the auxiliary apparatus whereas theamplificaiton of the lower frequencies is left to a component pertainingto the radio receiver means.

References Cited in the file of this patent UNITED STATES PATENTS2,273,866 Holst Feb. 24, 1942 2,559,354 Gauthier July 3, 1951 2,922,848Miller Jan. 26, 1960 FOREIGN PATENTS 837,430 France Feb. 9, 1939

